The primary objective of this study is to determine if there are identifiable parameters or risk factors that can be quantitated and used as predictors of hypertension proneness in a population of young Black Americans. A secondary objective is to clarify the prognosis of casual or labile high blood pressure. The study is designed as a long-term prospective study but the data gathered in the initial years will have immediate significance. The following will be investigated: The role of catecholamines in hypertensive and prehypertensive individuals. Dopaminebeta hydroxylase activity will be used as one index of catecholamine turnover rates. Familial patterns and genetic aspects will be explored. The effect of emotional and mental stress on blood pressure and catecholamine excretion will be studied using real life and other types of stress. Echocardiographic studies of cardiac dynamics will be conducted in normals, hypertensive prone and hypertensive subjects. The dietary problem with special reference to salt-intake will be studied. The value of random plasma renin determination as a predictor of hypertension and its complications, plus the profile of plasma renin in normal subjects, hypertensive subjects and first degree relatives of hypertensive patients will be determinea. Other factors to be studied are obesity, cigarette smoking, tachycardia, response to tilt test, response to static and dynamic exercise and blood pressure and renin response to the cold pressor test.